1. Field of the Invention:
The present invention relates to light scattering photometers for making multiple measurements simultaneously and, more particularly, to apparatus permitting the simultaneous measurement of light at two different angles in a photometer.
2. Description of the Prior Art:
Inhomogeneity in the indices of refraction of particulates in natural waters leads to scattering of an incident beam of light, the intensity of the scattered light varying with its angular relationship to the optical axis of the incident beam. It has been found that particulates present in sea water having a high index of refraction, substantially 1.15 relative to water, characteristic of inorganic materials such as silica or calcium carbonate and organic skeletal material, tend to scatter light at large angles, greater than 80.degree.. On the other hand, particulates in sea water having a low index of refraction, 1.01 to 1.05 relative to water, characteristic of organic material, play a strong role in the scattering of light at smaller angles, 1.degree. to 10.degree.. These results suggest that a scattering photometer capable of simultaneously observing the light scattered at a small angle of scattering, 1.degree. to 10.degree., and at a large angle of scattering, greater than 80.degree., could distinguish between the low and high index particulate matter present in natural waters and industrial streams.
Known prior art scattering photometers are incapable of simultaneous measurement of light scattered at both a small angle of scattering and a large angle of scattering. Additionally, they are incapable of continuous operation while a liquid suspension or hydrosol is being pumped through the scattering cell, as would be the case for example, if the photometer were operated aboard a ship underway. Furthermore, these instruments are large and bulky and incapable of considerable miniaturization.